PROJECT SUMMARY Pharmacologic targeting of oncogenic protein interactions remains the holy grail of developmental therapeutics research and holds promise to deliver a new era of treatments for human cancer. Whereas small molecule drug discovery continues to deliver effective agents for targeting deep, hydrophobic holes in protein targets such as kinase sites, the large, flat, and complex terrain that characterizes dynamic protein interaction surfaces remains largely undrugged. My work as a Senior Research Scientist in the Walensky laboratory and Linde Program in Cancer Chemical Biology at the Dana-Farber Cancer Institute involves an alternative approach to dissecting and targeting cancer protein interactions using hydrocarbon-stapled peptides, which recapitulate the shape, stability, and bioactivity of natural ?-helical interaction motifs embedded within signaling proteins. Our research programs focus on generating stapled peptides to elucidate the functional binding surfaces and interaction mechanisms that drive the apoptotic blockades and pathologic transcriptional programs of human cancer, emphasizing deregulated BCL-2 family, p53, and KRAS signal transduction. We strive to continually broaden the utility of peptide stapling by adapting these novel reagents for proteomic discovery, structural analyses, cellular mechanism of action studies, and in vivo application. Through a series of collaborations, we have also deployed stapled peptides in diverse cancer contexts, studying and targeting oncogenic ?-catenin, EZH2/EED, Olig2, MUC1-C, ATF2, and RPA. In each of these projects, new mechanistic insights and prototype therapeutics have emerged. Our photoreactive stapled peptides designed for protein capture, rapidly identify and map binding sites on known and unanticipated protein targets, expanding the potentially druggable cancer proteome. Indeed, the clinical potential of stapled peptides as a new drug modality for cancer is reflected by ongoing clinical trials of the first dual inhibitor of HDM2/HDMX for reactivating p53 in advanced solid tumors and lymphomas (NCT02264613). Over the last ten years, I have led the stapled peptide synthesis facility of the Walensky laboratory and Linde Program in Cancer Chemical Biology. In doing so, I have been personally responsible for developing and optimizing the chemistry behind stapled peptide synthesis, and creating an integrated consultation, production, purification, quantitation, and characterization workflow that has fueled diverse applications and clinical translation of stapled peptides. My graduate training in chemistry, my postdoctoral work at the intersection of chemistry and cancer biology, and my numerous and multidisciplinary collaborative experiences as a Dana-Farber Research Scientist, underlie my tremendous enthusiasm for harnessing the potential of next-generation stapled peptides to impact both our understanding and treatment of human cancer.